Time spent in vigorous physical activity is associated with increased exhaled nitric oxide in non-asthmatic adolescents.

Introduction: Physical activity (PA) is important in preventing disease, but endurance elite athletes have increased prevalence of asthma and airway inflammation.

Objectives: We aimed to determine if PA was associated with increased fractional exhaled nitric oxide (FENO ) in asthmatic and non-asthmatic adolescents.

Methods: FENO was recorded (Niox Mino®, Aerocrine AB, Stockholm, Sweden) in 169 adolescents (13-14 years) in a nested case-control analysis from the Environment and Childhood Asthma study, Oslo, 92 adolescents with and 77 without asthma. They underwent clinical examination, lung function measurements and treadmill run measuring peak oxygen uptake, and objectively recorded PA for four consecutive days. PA was classified as moderate, vigorous and very vigorous, and total number of hours of each category was recorded for each subject. Associations between FENO and PA were tested using linear robust multiple regression analyses.

Results: In non-asthmatic adolescents, FENO was associated with daily hours of vigorous to very vigorous (r=0.27, P=0.02) and very vigorous PAs (r=0.25, P=0.036) in bivariate analyses. In multivariate analyses, FENO was associated with vigorous to very vigorous PA [regression coefficients (95% confidence interval) 1.9 (0.6, 3.1); P=0.004] and more strongly with very vigorous PA [3.9 (1.5, 6.4); P=0.002] in non-asthmatic but not in asthmatic adolescents. Total daily PA was not associated with FENO in either group. Thus, 1 h of very vigorous PA per day increased FENO by 3.9ppb.

Conclusion: Vigorous to very vigorous PA, contrasting total daily PA, was significantly associated with increased FENO in non-asthmatic adolescents, suggesting that intensive PA may induce airway inflammation independent of asthma.